A switched-mode power converter (also referred to as a “power converter”) is a power supply or power processing circuit that converts an input voltage waveform into a specified output voltage waveform. A power factor correction (“PFC”) power converter includes a power train with a PFC stage that is generally followed by a regulation and isolation stage. The power converter is coupled to a source of electrical power (an alternating current (“ac”) power source) and provides a direct current (“dc”) output voltage. The PFC stage receives a rectified version of the ac input voltage (from the ac power source) and provides a dc bus voltage. The regulation and isolation stage employs the bus voltage to provide the dc output voltage to a load. The power converter including the PFC stage and the regulation and isolation stage can be employed to construct an “ac adapter” to provide the dc output voltage to a notebook computer or the like from the ac power source.
Controllers associated with the power converter manage an operation thereof by controlling conduction periods of power switches employed therein. Generally, the controllers are coupled between an input and an output or coupled to terminals associated with internal characteristics such as an internal bus voltage of the power converter in a feedback loop configuration (also referred to as a “control loop” or “closed control loop”).
A PFC power converter is frequently constructed with two interleaved boost switching regulators, which is a circuit configuration that is frequently employed to reduce input and output ripple currents and the size of filters that are needed to meet an electromagnetic interference requirement. Average current-mode control is also frequently employed to regulate a characteristic of the power converter, such as an internal bus voltage or output voltage thereof. Controlling an average value of a current in a boost switching regulator such as an average current in a boost inductor generally produces better harmonic distortion and power factor correction performance than controlling the peak value of a current therein.
However, conventional techniques to control an average value of a current in a PFC power converter formed with two interleaved boost switching regulators generally produces unequal currents in the two interleaved boost switching regulators. Unequal currents generate a higher level of input and output ripple currents, which degrades the electromagnetic interference performance of the PFC power converter.
Accordingly, what is needed in the art is a controller that produces substantially equal currents in a power train formed with two interleaved boost switching regulators to avoid the deficiencies in the prior art.